1. Field of the Invention
The present invention is directed generally to a semiconductor laser arrangement, and more particularly an arrangement of two semiconductor lasers wherein one predominately generates or amplifies waves of a defined polarization state and the other predominately generates or amplifies waves of a defined other polarization state wherein the waves generated or amplified by the two lasers are superimposed on one another.
2. Description of the Related Art
Optical amplifiers or laser amplifiers that can isotropically amplify polarized light are required in modern systems for applications in optical communications technology. To isotropically amplify denotes that light having an arbitrary polarization can be amplified with the same gain independently of the polarization. In a semiconductor laser having a light-intensifying layer, the optical amplification or intensification, is usually greatly dependent on the polarization of the light being amplified. For example, light polarized in the plane of the layer is amplified relatively greatly while light polarized perpendicularly relative to the plane is amplified relatively weakly, or not at all.
An isotropic amplification can be achieved in that the polarized light to be amplified is coupled into two semiconductor lasers arranged in series with or parallel to one another. The layers of the lasers which have the light-intensifying effect lie in planes arranged vertically relative to one another and have the same gain. An arrangement of this type is known from ECOC, 1987, pages 87-88. In this arrangement, the layer of a semiconductor laser that has a light-intensifying effect lies in the oscillatory plane of the TE mode, whereas the corresponding layer of the other semiconductor amplifier lies in the oscillatory plane of the TM mode that is polarized orthogonally relative to the TE mode. The two semiconductor lasers of this known arrangement can be joined to one another by passive, optical waveguides that preserve the polarization state. The delivery of the polarized light to be amplified as well as the further conduction of the amplified light can ensue with such waveguides.